A variety of different paving machines are used in construction and related industries for depositing a mat of paving material, typically an asphalt material, on a work surface. Such machines are usually self-propelled, and include a receptacle for paving material, a screed for distributing and compacting the paving material on a work surface, and a conveyor which transfers paving material from the receptacle to the screed. One feature common to most types of paving machines is an adjustable support apparatus for the screed which is coupled with a frame of the paving machine and can be used to elevate the screed from a lowered, paving position to a higher position for transport. Since part of the function of screeds is to compact paving material, they are typically relatively heavy. Screeds are often 25% or more of the total weight of an associated paving machine. In the lowered position, much of the weight of the screed is supported by the work surface, riding or “floating” on the paving material distributed by the paving machine. When in the raised position, the screed does not rest on the work surface and its full weight is typically borne by the support apparatus.
When a paving machine is adjusted from a state at which the screed is lowered to a state at which the screed is raised, a center of gravity of the paving machine can change significantly. In particular, when the screed is lowered, and much or all of its weight supported by the work surface, the center of gravity of the paving machine tends to be relatively further forward. This phenomenon is generally opposite to what is desirable, as weight toward the back end could improve traction when the screed is lowered. When the screed is raised, the center of gravity tends to move towards the back of the machine. This is also generally opposite to what is desirable, as machine stability can suffer, hindering travel and possibly violating jurisdictional requirements for public roads and the like.
In an effort to design a machine which can reliably have sufficient traction for paving, but also stability for driving the machine when not paving, engineers have typically added extra weight strategically at certain locations on the paving machine. It is common for back tires of a paving machine to be filled with liquid, such as water, propylene glycol, etc. Solid steel plates may also be affixed to paving machines at locations towards their front end. Adding extra, fixed mass can lessen the extent to which the center of gravity changes when moving the screed between a raised position and a lowered position, and can help ensure that sufficient weight remains in appropriate positions in different machine states. While these strategies have been successful, there remains ample room for improvement.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.